U.S. patent number 4,275,344 [Application Number 06/073,243] was granted by the patent office on 1981-06-23 for voltage control apparatus for electric generators for vehicles.
This patent grant is currently assigned to Nippondenso Co., Ltd.. Invention is credited to Yoshio Akita, Taro Asahi, Keiichiro Banzai, Katsumi Itoh, Katsutaro Iwaki, Akira Mase, Kazumasa Mori, Katsuya Muto, Takayasu Nimura.
United States Patent |
4,275,344 |
Mori , et al. |
June 23, 1981 |
Voltage control apparatus for electric generators for vehicles
Abstract
In a voltage control apparatus for an electric generator (1) for
vehicles including an armature winding (3), an exciting coil (4), a
rectifier (2) for rectifying an a.c. output from the armature
winding, and a voltage regulator (5), the voltage regulator
comprises a differential amplifier circuit (26) producing a
detected voltage corresponding to a difference between a battery
charging voltage and a reference voltage, a comparator circuit (30)
comparing the detected voltage with a triangular waveform voltage
generated at constant periods and producing a pulsed output
voltage, a first driver circuit (51) effecting duty-factor-control
of an exciting current flowing through the exciting coil in
response to the pulsed output voltage, and an initial excitation
circuit (32) for causing a predetermined small initial exciting
current to flow through the exciting coil intermittently during a
time interval after the start of the electric generator.
Inventors: |
Mori; Kazumasa (Aichi,
JP), Asahi; Taro (Chiryu, JP), Banzai;
Keiichiro (Toyota, JP), Iwaki; Katsutaro (Chiryu,
JP), Muto; Katsuya (Kariya, JP), Mase;
Akira (Handa, JP), Nimura; Takayasu (Nagoya,
JP), Itoh; Katsumi (Oobu, JP), Akita;
Yoshio (Ichinomiya, JP) |
Assignee: |
Nippondenso Co., Ltd. (Kariya,
JP)
|
Family
ID: |
14546883 |
Appl.
No.: |
06/073,243 |
Filed: |
September 6, 1979 |
Foreign Application Priority Data
|
|
|
|
|
Sep 8, 1978 [JP] |
|
|
53-110874 |
|
Current U.S.
Class: |
322/28; 322/60;
322/73; 361/21; 320/123; 320/164 |
Current CPC
Class: |
H02P
9/305 (20130101); H02J 7/2434 (20200101); Y02T
10/70 (20130101); Y02T 10/92 (20130101); Y02T
10/7005 (20130101) |
Current International
Class: |
H02J
7/16 (20060101); H02J 7/24 (20060101); H02P
9/14 (20060101); H02P 9/30 (20060101); H02P
009/30 () |
Field of
Search: |
;322/28,59,61,60,69,70,99,72,73 ;320/61,62,64 ;361/20,21 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truhe; J. V.
Assistant Examiner: Redman; John W.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
We claim:
1. A voltage control apparatus for electric generators for vehicles
comprising:
an electric generator having an armature winding, an exciting coil
and a rectifier for rectifying an a.c. output from said armature
winding;
a battery charged by a d.c. output from said rectifier;
a voltage detecting circuit detecting a generated voltage of said
electric generator or a charging voltage of said battery and
producing an output detected voltage;
a reference voltage circuit for generating a reference voltage
representing a desired value for a battery voltage to be
regulated;
a differential amplifier circuit receiving the output detected
voltage from said voltage detecting circuit and the reference
voltage from said reference voltage circuit as input signals
thereto and producing a difference voltage obtained by difference
amplification;
a triangular waveform generator circuit generating a triangular
waveform voltage within a predetermined range of swing and at
constant periods;
a comparator circuit receiving the difference voltage from said
differential amplifier circuit and the triangular waveform voltage
from said triangular waveform generator circuit, comparing the two
voltages with each other, and producing an output signal;
a first driver circuit for energizing said exciting coil in
response to the output signal from said comparator circuit; and
an initial excitation circuit for forcibly causing an oscillation
signal for initial excitation to be generated and supplying the
oscillation signal to said first driver circuit to make said first
driver circuit supply an initial exciting current to said exciting
coil during a time interval from the start of said electric
generator to the arrival thereof at a predetermined condition of
electric generation.
2. A voltage control apparatus for electric generators for vehicles
according to claim 1, wherein the difference voltage from said
differential amplifier circuit increases or decreases from the
reference voltage depending on the relative magnitude of the
battery charging voltage and the desired value for a battery
voltage to be regulated.
3. A voltage control apparatus for electric generators for vehicles
according to claim 1, wherein the magnitude of the difference
voltage from said differential amplifier circuit becomes equal to a
minimum value and a maximum value of said triangular waveform
voltage within the range of voltage regulation of .+-.1.3%-2.1% of
a battery charging voltage taken on the basis of the desired value
for a battery voltage to be regulated, respectively.
4. A voltage control apparatus for electric generators for vehicles
according to claim 1, further comprising an overvoltage detecting
circuit for detecting the occurrence of an overvoltage, which
exceeds a predetermined voltage, and producing an overvoltage
detection signal.
5. A voltage control apparatus for electric generators for vehicles
according to claim 1, wherein said first driver circuit comprises a
first switching circuit having an output terminal connected to said
exciting coil and operating to switch an exciting current supplied
to said exciting coil and a first protective circuit for detecting
the appearance of an abnormal high voltage at the output terminal
of said first switching circuit to render said first switching
circuit inoperative.
6. A voltage control apparatus for electric generators for vehicles
according to claim 4, wherein said first driver circuit comprises a
first switching circuit having an output terminal connected to said
exciting coil and operating to switch an exciting current supplied
to said exciting coil and a first protective circuit for rendering
said first switching circuit inoperative upon detection of the
appearance of an abnormal high voltage at the output terminal of
said first switching circuit or upon receipt of the overvoltage
detection signal from said overvoltage detecting circuit.
7. A voltage control apparatus for electric generators for vehicles
according to claim 1, further comprising a battery temperature
detecting device for detecting temperatures of said battery and
producing a battery temperature detection signal and a temperature
compensation circuit receiving the battery temperature detection
signal from said battery temperature detecting device and producing
a battery temperature compensation voltage for modifying the
reference voltage generated by said reference voltage circuit.
8. A voltage control apparatus for electric generators for vehicles
according to claim 4, further comprising a third driver circuit for
driving indicating means to indicate whether an initial generated
voltage of said electric generator by initial excitation of said
exciting coil has reached a predetermined value and to warn a
driver of the generation of an overvoltage by said electric
generator when said overvoltage detecting circuit has produced the
overvoltage detection signal.
9. A voltage control apparatus for electric generators for vehicles
according to claim 1 or 8, further comprising a second driver
circuit having an external output terminal producing an electrical
output whose electric potential takes a low level or a high level
depending on whether an initial generated voltage of said electric
generator by initial excitation of said exciting coil has reached a
predetermined value.
10. A voltage control apparatus for electric generators for
vehicles according to claim 8, wherein said third driver circuit
has an external output terminal and comprises a third switching
circuit whose output is connected to the external output terminal
of said third driver circuit and a third protective circuit for
detecting the appearance of an abnormal high voltage at the
external output terminal of said third driver circuit to render
said third switching circuit inoperative.
11. A voltage control apparatus for electric generators for
vehicles according to claim 9, wherein said second driver circuit
has an external output terminal and comprises a second switching
circuit whose output is connected to the external output terminal
of said second driver circuit and a second protective circuit for
detecting the appearance of an abnormal high voltage at the
external output terminal of said second driver circuit to render
said second switching circuit inoperative.
Description
This invention relates to a voltage control apparatus for electric
generators for vehicles each of which electric generators comprises
an exciting coil. Especially, this invention relates to a voltage
control apparatus which enables suitable initial excitation and
makes an initial excitation resistor unnecessary and which also
enables high precision voltage control by performing a voltage
detecting operation always at predetermined periods and effecting
suitable duty factor control of an exciting current
Generally, conventional voltage control apparatuses for electric
generators for vehicles have a construction such that one desired
value for a voltage to be regulated (hereinafter abbreviated as
"desired voltage") is predetermined beforehand and the generated
voltage is compared with the desired voltage to discriminate
whether the former is higher or lower than the latter and thereby
to effect selective control of either conduction or nonconduction
of an exciting current through an exciting coil. However, with the
apparatuses of the abovementioned principle of voltage control it
sometimes occurs that, in a case where the rotational speed of the
electric generator is low or under some condition of electric load,
a generated voltage is apt to depart from the predetermined desired
voltage due to a time delay in the response of the voltage control
system, etc., and besides, once a generated voltage has departed
away from the predetermined desired voltage, it is difficult for a
generated voltage to settle down promptly to the predetermined
desired voltage, causing it to fluctuate with a long period
(generally called the phenomenon of "hunting"), thus making it
impossible to effect the voltage control with favourable precision.
This fact offers a serious problem when an operating system such as
a microcomputer or the like, which requires a power supply
regulated with high precision, is installed on a vehicle and
connected as an electric load. Nevertheless, it is expected that
voltage control with high precision will be required more and more
in the future.
Further, it is a recent tendency to fabricate voltage control
apparatuses for electric generators for vehicles using integrated
semiconductor circuits (hereinafter abbreviated as "IC"). However,
voltage control apparatuses used presently comprise an initial
excitation resistor of a relatively high power rating connected in
series with a current supply circuit for an exciting coil in order
to prevent overdischarge of a battery by limiting an exciting
current to a possible minimum value in the stage of initial
excitation of an electric generator. Thus, this fact makes it
impossible to fabricate that portion in an IC and forms a factor to
incur high cost.
This invention has been made in view of the above-mentioned problem
and aims at providing a voltage control apparatus for electric
generators for vehicles which is designed to effect suitable
initial excitation and to make an initial excitation resistor
unnecessary and which enables to control, with higher precision, a
generated voltage or a battery charging voltage from an electric
generator driven by a vehicle-mounted engine throughout the entire
range of its rotational speeds.
One of the features of this invention resides in that a detected
voltage corresponding to a difference between a generated voltage
or a battery charging voltage and a reference voltage is compared
with a triangular waveform voltage generated at constant periods,
and duty-factor-control of an exciting current is effected always
at constant periods depending on the relative magnitude of the
above-mentioned voltages.
Further, another feature of this invention resides in that an
exciting coil is energized intermittently in response to an
oscillating signal having a predetermined repetition period during
a time interval from the switching-on of a key switch to a moment
when the electric generator reaches a predetermined generating
state thereby to limit an average value of the exciting current to
a degree necessary to assure the build-up of the electromotive
force (hereinafter simply termed "the build-up") of the electric
generator.
This and other objects, features and advantages of the present
invention will be made apparent from the following descriptions
taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a general circuit diagram showing an embodiment of the
apparatus of this invention;
FIG. 2 is a block diagram showing a concrete embodiment of the
apparatus of this invention;
FIGS. 3 and 4 are, respectively, a signal waveform diagram and a
control characteristic diagram for illustrating the operation of
the apparatus of this invention;
FIGS. 5 to 9 are electric circuit diagrams showing concrete
examples of the electric circuits of the apparatus of this
invention; and
FIG. 10 is an electric circuit diagram showing another embodiment
of the apparatus of this invention.
An explanation will hereinafter be given of this invention with
respect to the embodiments thereof shown in the drawings. FIG. 1 is
a circuit diagram showing the general construction of the apparatus
of this invention. Numeral 1 designates an electric generator
driven by an engine mounted on a vehicle. It will be simply termed
"generator" in the following descriptions. The generator 1
comprises an armature coil 3, an exciting coil 4 for exciting the
generator 1 and a full-wave rectifier 2. The generator 1 shown here
produces a d.c. output obtained through the rectification of a
three-phase a.c. voltage generated in the Y-connection armature
winding 3. Numeral 5 designates a voltage regulator provided with
various input and output terminals. The voltage regulator 5 mainly
effects the control of energization of the exciting coil 4 and an
indicating means 8 for indicating a state of electric generation by
the generator 1. Numeral 6 designates a battery mounted on the
engine, 7 a key switch, 8 the electric generation indicating means
comprising a lamp, a light-emitting diode, etc., and 9 a battery
temperature detecting device which comprises a temperature
detecting element, such as thermistor, a heat-sensitive diode,
etc., disposed in the electrolyte of the battery or attached to a
portion of the body of the battery and outputs an electric signal
whose level varies in response to detected temperatures. The
construction of the electric circuit block of the voltage regulator
5 in this embodiment of the invention is designed with a view to
fabricating it in the form of IC.
Next, the detailed construction of the voltage regulator 5 will be
described hereinafter in conjunction with the illustration of FIG.
2. Firstly, with respect to the various kinds of input and output
terminals of the voltage regulator 5, symbol "B.sub.o " designates
an input terminal for inputting a voltage generated by the
generator 1 as a detected voltage, "L.sub.1 " an output terminal
which develops a low output impedance and drives the indicating
means 8, "L.sub.2 " an output terminal for outputting an electric
generation indicating signal which shows that the build-up of a
voltage generated by the generator 1 has been completed, "IG" an
input terminal which receives a power source voltage from an
ignition terminal of the key switch 7 when it has been closed,
"S.sub.V " an input terminal for detecting an inputting a battery
charging voltage, "S.sub.T " an input terminal for inputting a
signal responding to temperatures of the battery 6, "N" an input
terminal for detecting the state of electric generation by the
generator 1, namely, for inputting a voltage of the neutral point
of the armature winding of the alternator 1 in this case, "E" an
input terminal for inputting a ground potential, and "F" an output
terminal for controlling an exciting current flowing through the
exciting coil 4.
Then, referring to the block diagram of FIG. 2 showing the
construction of the voltage regulator 5, numeral 21 designates a
charging voltage detecting circuit, which inputs a generated
voltage and a battery charging voltage V.sub.B at its terminals
B.sub.o and S.sub.V, respectively, and outputs normally a voltage
responding to a battery charging voltage V.sub.B, but outputs a
voltage responding to a generated voltage received at the terminal
B.sub.o when it has become impossible to receive a battery charging
voltage V.sub.B at the terminal S.sub.V due to a contact failure
occurring at the terminal S.sub.V or the breakage of an input
connection wire to the terminal S.sub.V. Numeral 22 designates a
temperature compensation circuit receiving a detection signal which
the battery temperature detecting device 9 supplies to the terminal
S.sub.T of the voltage regulator 5 and operating to modify a
reference voltage generated in a reference voltage circuit 25 in
response to the above-mentioned detection signal, thereby imparting
a necessary temperature characteristic to a voltage to be regulated
by the voltage regulator 5. This necessary temperature
characteristic is to make the battery charging characteristic
approach, as closely as possible, an ideal temperature versus
charging voltage characteristic of the battery within a limited
voltage range required by the vehicle. Numeral 23 designates an
electric generation detecting circuit which inputs a neutral point
voltage of the generator 1 received at the terminal N in this case
and generates an electric generation signal when it detects that
the neutral point voltage has reached a predetermined value which
presumes the completion of the build-up of a voltage generated by
the generator 1.
Numeral 24 designates a voltage detecting circuit which comprises a
smoothing element such as a capacitor, etc. at its input stage. The
voltage detecting circuit 24 receives an output voltage of the
charging voltage detecting circuit 21 and smooths it to some degree
and outputs a detected voltage V.sub.S obtained by dividing the
input voltage at a predetermined ratio. Numeral 25 designates a
reference voltage circuit which divides a constant voltage V.sub.c
supplied from a power supply circuit 42 at a predetermined ratio
and generates a reference voltage V.sub.o which has been
temperature-compensated by an output signal of the temperature
compensation circuit 22 as described before. Numeral 26 designates
a differential amplifier circuit which receives a detected voltage
V.sub.S from the voltage detecting circuit 24 and a reference
voltage V.sub.o from the reference voltage circuit 25 as input
signal voltages thereto and amplifies a difference between both
input signal voltages at a predetermined amplification degree to
output a resultant detected voltage V.sub.D. Numeral 27 designates
a triangular waveform generator circuit which receives a power
supply from the power supply circuit 42 and generates a triangular
waveform voltage of a predetermined frequency (about 50-100 Hz).
Numeral 28 designates an overvoltage detecting circuit which
monitors an output voltage from the charging voltage detecting
circuit 21 and outputs an overvoltage detection signal when it has
detected that the output voltage of the charging voltage detecting
circuit 21 has taken an excessively high value which is considered
to be abnormal. Numeral 29 designates a waveform shaping circuit
which detects an instant when a triangular waveform voltage, which
is supplied from the triangular waveform generator circuit 27,
reaches a preset level and forms a pulse signal having a
predetermined duty ratio. Numeral 30 designates a comparator
circuit which inputs a detected voltage V.sub.D from the
differential amplifier circuit 26 and a triangular waveform voltage
from the triangular waveform generator circuit 27 and generates a
comparison signal depending on the relative magnitude of both
voltages. Numeral 31 designates a frequency divider circuit which
divides the frequency of a pulse signal supplied from the waveform
shaping circuit 29 to form a pulse signal having a frequency (about
1-10 Hz) which permits assured perception of a flashing operation
of an indicating means. Numeral 32 designates an initial excitation
circuit which receives a pulse signal from the waveform shaping
circuit 29 and an electric generation signal from the electric
generation detecting circuit 23 and generates an initial excitation
intermitting command signal which commands to energize
intermittently the exciting coil 4 in response to the state of "H"
or "L" level of a pulse signal from the waveform shaping circuit 29
during a time interval from the switching-on of the key switch 7 to
the reception of an electric generation signal.
Numeral 33 designates a logic circuit which inputs a pulse signal
from the frequency divider circuit 31, an electric generation
signal from the electric generation detecting circuit 23 and an
overvoltage detection signal from the overvoltage detecting circuit
28 and generates a lighting command signal during a time interval
from the switching-on of the key switch 7 to the reception of an
electric generation signal. On the other hand, the logic circuit 33
outputs a pulse signal supplied from the frequency divider circuit
31 as a flashing command signal while the logic circuit 33 is
receiving an overvoltage detection signal.
Numeral 51 designates a first driver circuit which comprises a
first protective circuit 34 and a first switching circuit 35 and
inputs a comparison signal from the comparator circuit 30 and an
initial excitation intermitting command signal from the initial
excitation circuit 32. Especially, when an initial excitation
intermitting command signal has been received, the first driver
circuit 51 responses to the initial excitation intermitting command
signal in preference to a comparison signal and drives the first
switching circuit 35 to control intermittent energization of the
exciting coil 4. But, after the initial excitation intermitting
command signal has ceased, the first driver circuit 51 drives the
first switching circuit 35 depending on the state of "H" or "L"
level of a comparison signal received. The first protective circuit
34 monitors an electric potential of each of a comparison signal,
an initial excitation intermitting command signal, and the output
terminal F of the first driver circuit 51. If a power source
voltage is impressed by accident on the output terminal F due to
short-circuit of the exciting coil 4, etc. while the first
switching circuit 35 is in operation (that is, when the first
switching circuit 35 is in a state of drawing an electric current),
the first protective circuit 34 immediately causes the first
switching circuit 35 to stop its operation and prevents a
transistor in the output stage of the first switching circuit 35
from being destroyed by a possible excessive current. Now, it
should be noted that the term "an electric current drawing state"
used here represents that a portion of an electric circuit is at a
potential of zero or negative level and in a state ready to draw an
electric current from the outside, on the other hand, the term "an
electric current supplying stage" used here represents that a
portion of an electric circuit is at a potential of positive level
and in a state ready to supply an electric current to the outside.
Further, the first protective circuit 34 is constructed to input an
overvoltage detection signal from the overvoltage detecting circuit
28 and to cause the first switching circuit 35 to stop its
operation upon appearance of an overvoltage.
Numeral 52 designates a second driver circuit which comprises a
second protective circuit 36 and a second switching circuit 37 and
inputs an electric generation signal from the electric generation
detecting circuit 23. The second driver circuit 52 puts its output
terminal L.sub.2 in an electric current supplying state during a
time interval from the switching-on of the key switch 7 to the
reception of an electric generation signal, on the other hand, puts
its output terminal L.sub.2 in an electric current drawing state
while the second driver circuit 52 is receiving an electric
generation signal. Namely, it is possible to supply a signal from
the output terminal L.sub.2 in response to the states of electric
generation of the generator 1. Therefore, if an external load is
connected to the output terminal L.sub.2, it is possible to supply
a check signal or a drive command signal to the external load in
response to the states of electric generation of the generator 1.
Further, the second protective circuit 36 has the same function as
that of the above-described first protective circuit 34. If a power
source voltage or a ground potential is impressed by accident on
the output terminal L.sub.2 when the second switching circuit 37 is
in operation, namely, when the second switching circuit 37 is in an
electric current drawing or supplying state, the second protective
circuit 36 immediately causes the second switching circuit 37 to
stop its operation and prevents a heavy current from flowing
through a transistor in the output stage of the second switching
circuit 37.
Numeral 53 designates a third driver circuit which comprises a
third protective circuit 38 and a third switching circuit 39. When
the third driver circuit 53 receives a lighting command signal or a
flashing command signal from the logic circuit 33, the third
switching circuit 39 operates to cause the indicating means 8 to be
lighted or flashed. Further, the third protective circuit 38
operates in the same way as the first and second protective
circuits 34 and 36, respectively, and if a power source voltage is
impressed by accident on the output terminal L.sub.1 of the third
driver circuit 53 when it is in an electric current drawing state,
the third protective circuit 38 operates to stop the operation of
the third switching circuit 39.
Numeral 40 designates a switching-on detecting circuit which
responds to the operation of the key switch 7. When the key switch
7 is switched on and a battery voltage (or a power source voltage)
is applied normally to the terminal IG, the switching-on detecting
circuit 40 supplies a battery voltage to a power supply circuit 42
and simultaneously stops the operation of a terminal connection
failure detecting circuit 41. If a battery voltage is not supplied
to the switching-on detecting circuit 40 due to a connection
failure occurring at the terminal IG, etc. despite that the key
switch 7 has been switched on, no operation stopping signal is sent
from the switching-on detecting circuit 40 to the terminal
connection failure detecting circuit 41. In such a case, the
terminal connection failure detecting circuit 41 operates to supply
a battery voltage to the power supply circuit 42 via the indicating
means 8 and the circuit 41 itself. At this time, the terminal
connection failure detecting circuit 41 sends an inhibit signal to
the third driver circuit 53 to prevent it from being put into an
electric current drawing state. Thus, the power supply circuit 42
produces a constant voltage stabilized by a constant voltage
element and supplies the constant voltage (5 to 8 volts, for
example) to each circuit in the circuit block 60 shown in FIG. 2.
Here, it may be possible to make the terminal connection failure
detecting circuit 41 receive an electric generation voltage through
the charging voltage detecting circuit 21, as shown by a broken
line in FIG. 2, instead of receiving a battery voltage via the
indicating means 8.
The operation of the apparatus of this invention having the
above-described construction will be explained hereinafter.
Firstly, before the key switch 7 is closed, no power source voltage
is supplied to the voltage regulator 5, and the terminals F,
L.sub.1 and L.sub.2 remain in an open or de-energized state.
Then, when the key switch 7 has been closed, a power source voltage
is supplied to the voltage regulator 5 through the terminal IG to
cause the switching-on detecting circuit 40 and the power supply
circuit 42 to be operative, and the latter circuit 42 supplies a
constant voltage to each circuit in the circuit block 60 in FIG. 2.
If no power source voltage is supplied to the switching-on
detecting circuit 40 due to a connection failure, coming-off of a
connecting wire, etc. occurring at the terminal IG, then the
terminal connection failure detecting circuit 41 operates and a
power source voltage is supplied to the power supply circuit 42 via
the terminal connection failure detecting circuit 41 and the
indicating means 8 or the charging voltage detecting circuit
21.
Since the generator 1 is not yet in a state of electric generation
before the engine starts its operation, the electric generation
detecting circuit 23 detects that the generator 1 is still in an
inactive state and continues to output a non-electric-generation
signal, thereby causing the initial excitation circuit 32 to be
operative. Therefore, the initial excitation circuit 32 applies to
the first driver circuit 51 an initial excitation intermitting
command signal in response to a pulse signal from the waveform
shaping circuit 29 to control intermittent energization of the
exciting coil 4. Further, in the intermittent energization control,
the duty factor or the conduction rate of the initial excitation
intermitting command signal is preset to limit an average value of
an initial exciting current flowing through the exciting coil 4 to
a low degree (about 300 mA) still permitting the build-up of the
generator 1. Further, the signal representing a state of
non-electric-generation from the electric generation detecting
circuit 23 is supplied also to the second driver circuit 52 and the
logic circuit 33, whereby the second driver circuit 52 puts its
output terminal L.sub.2 in an electric current supplying state
representing a state of non-electric-generation, and, on the other
hand, the logic circuit 33 outputs a pulse signal, which it has
received from the frequency divider circuit 31, to cause the third
driver circuit 53 to operate and thereby to drive the indicating
means 8 to be lighted.
Now, when the engine has started its operation, the rotor of the
generator 1 is driven to rotate, and the electromotive force of the
generator 1 starts to build up due to an initial exciting current
as described before, and the neutral point voltage of the generator
1 also starts to build up. The electric generation detecting
circuit 23 detects the build-up of the neutral point voltage, and
it outputs an electric generation signal when the neutral point
voltage has reached a predetermined value. Then, the initial
excitation circuit 32 stops to generate an initial excitation
intermitting command signal, the second driver circuit 52 puts its
output terminal L.sub.2 in an electric current drawing state
representing a state of electric generation, and the third driver
circuit 53 puts its output terminal L.sub.1 in a high impedance
state representing a state of electric generation and causes the
indicating means 8 to stop its operation.
Next, since the initial excitation circuit 32 stops its operation,
the first driver circuit 51 controls energization of the exciting
coil 4 in response to a comparison signal from the comparator
circuit 30. Next, an explanation will hereinafter be made of the
excitation control system by the use of a triangular waveform
voltage in conjunction with the signal waveform diagram of FIG.
3.
Upon switching-on of the key switch 7, the triangular waveform
generator circuit 27 is supplied with a power supply voltage and
starts its oscillating operation. But, this is still before the
start of the engine and the generator 1 has not yet started
electric generation. In this state, a battery voltage V.sub.B
(substantially 12 volts, for example) is supplied to the terminal
S.sub.V, and the divided output voltage V.sub.s of the voltage
detecting circuit 24 is smaller than the reference voltage V.sub.o
supplied from the reference voltage circuit 25 (V.sub.s
<V.sub.o). The differential amplifier circuit 26 generates a
detected voltage V.sub.D having a value which depends on a
difference between both input voltages. [V.sub.D =K(V.sub.o
-V.sub.s), where K is an amplification degree of the differential
amplifier circuit 26.] In this case, the detected voltages V.sub.D
takes a value V.sub.D1, as shown at (d) in the waveforms (A) of
FIG. 3, which is greater than a maximum voltage V.sub.2 of the
triangular waveform voltage from the triangular waveform generator
circuit 27, and the comparator circuit 30 outputs a comparison
signal voltage which is always at "H" level as shown by the
waveform (D) of FIG. 3. However, at this stage the initial
excitation circuit 32 is in operation causing an initial exciting
current to be supplied to the exciting coil 4, and the comparison
signal voltage from the comparator circuit 30 is disabled in the
first driver circuit 51.
Now, when the engine has started its operation, as a generated
voltage of the alternator 1 builds up gradually, a battery charging
voltage V.sub.B also rises and a divided output voltage V.sub.s of
the voltage detecting circuit 24 increases, so that the difference
between the divided voltage V.sub.s and the reference voltage
V.sub.o becomes smaller. If the comparator circuit 30 receives at
one of its input terminals a triangular waveform voltage shown at
(c) in the waveforms (A) of FIG. 3 and at the other one of its
input terminals a detected voltage V.sub.D2 shown at (a) in the
waveforms (A) of FIG. 3, for example, which is smaller than the
aforesaid detected voltage V.sub.D1 (V.sub.s <V.sub.o holds also
in this case,) the comparator circuit 30 outputs a pulsed voltage
shown at the waveform (B) of FIG. 3. The output stage transistor of
the first driver circuit 51 becomes conductive to energize the
exciting coil 4 when an output voltage of the comparator circuit 30
is at "H" level, for example, and, on the other hand, it becomes
nonconductive to de-energize the exciting coil 4 when an output
voltage of the comparator circuit 30 is at "L" level. Here, if a
battery charging voltage V.sub.B received at the terminal S.sub.V
is lower than a predetermined desired voltage, it is designed to
increase a conduction ratio in one period t.sub.2 /T (generally
termed "duty factor"), as shown by the waveform (B) of FIG. 3, and
to increase an average current flowing through the exciting coil 4,
thereby raising the excitation by the exciting coil 4.
If a generated voltage from the generator 1 further rises, a
battery charging voltage V.sub.B also rises and a divided voltage
V.sub.s in the voltage detecting circuit 24 increases. It is so
designed that, when a battery charging voltage V.sub.B exceeds the
predetermined desired voltage, a divided voltage V.sub.s becomes
greater than the reference voltage V.sub.o (V.sub.s <V.sub.o),
and hence a detected voltage V.sub.D3 from the differential
amplifier circuit 26 in this case becomes smaller than the
reference voltage V.sub.o . If the comparator circuit 30 receives
the detected voltage V.sub.D3 shown at (b) in the waveforms (A) of
FIG. 3, for example, which is lower than the reference voltage
V.sub.o shown at (f) in the waveforms (A) of FIG. 3 (V.sub.s
<V.sub.o holds in this case), the comparator circuit 30
generates an output voltage shown by the waveform (C) of FIG. 3. It
is seen that a conduction ratio t.sub.2 /T is made smaller
depending on the magnitude of a detected voltage V.sub.D to reduce
the magnitude of an average current flowing from an output stage
transistor in the first driver circuit 51 through the exciting coil
4, thus controlling a rise in the generated voltage of the
generator 1 by gradually reducing its excitation.
In the above case, it is designed that a detected voltage V.sub.D
becomes smaller than the reference voltage V.sub.o when a battery
charging voltage exceeds the predetermined desired voltage. In this
design, an operational amplifier in the differential amplifier
circuit 26 is supplied with a positive power supply. On the other
hand, if it is designed that the differential amplifier circuit 26
is supplied with a positive power supply and a negative power
supply, the differential amplifier circuit 26 may output a negative
voltage depending on a difference between two input voltages.
Next, if it is preset that a detected voltage V.sub.D takes a
ground potential, when a battery charging voltage V.sub.B exceeds
the predetermined desired voltage to a high degree by some cause,
and the triangular waveform generator circuit 27 generates a
triangular waveform voltage whose minimum voltage is a voltage
V.sub.1 shown in the waveforms (A) of FIG. 3 which is somewhat
above a ground potential, then the comparator circuit 30 receives
at one of its input terminals a detected voltage V.sub.D4 shown at
(e) in the waveforms (A) of FIG. 3 (V.sub.s <V.sub.o also holds
here) and generates an output voltage which is always at "L" level
as shown by the waveform (E) of FIG. 3. Accordingly, the output
stage transistor in the first driver circuit 51 becomes
nonconductive to render the exciting coil 4 de-energized. Further,
if a battery charging voltage rises to an extent which is
considered to be abnormal, the overvoltage detecting circuit 28
generates an overvoltage detection signal and causes the indicating
means 8 to be flashed through the logic circuit 33 and the third
driver circuit 53. On the other hand, if a battery charging voltage
becomes smaller than the predetermined desired voltage, a detected
voltage V.sub.D exceeds the voltage V.sub.1, which effects some
degree of excitation again and raises the battery charging voltage.
Thus, it is possible to regulate a battery charging voltage at the
predetermined desired value.
Further, if a connection wire is disconnected by accident from the
battery charging terminal while the excitation of the generator 1
is under way, a generation voltage of the generator 1 rises heavily
and instantly. In such a case, the overvoltage detecting circuit 28
detects the accident before the detection thereof by the voltage
detecting circuit 24, which has a comparatively big time delay, so
that it is possible to stop immediately the operation of the first
driver circuit 51 by an overvoltage detection signal produced by
the overvoltage detecting circuit 28.
As is understood from the foregoing explanation, it is arranged in
the above-described embodiment that the detected voltage V.sub.D,
which is an output voltage of the differential amplifier circuit
26, varies upward or downward with respect to the reference voltage
V.sub.o representing the predetermined desired voltage, so that the
detected voltage V.sub.D varies downward with respect to the
reference voltage V.sub.o when a battery charging voltage is higher
than the predetermined desired voltage. The width of variations of
the detected voltage V.sub.D is determined by an amplification
degree of the differential amplifier circuit 26, etc., especially
in consideration of the relation with the voltage swing (V.sub.2
-V.sub.1) of the triangular waveform voltage. Now, an explanation
will be given of a ratio (.DELTA.D/.DELTA.V.sub.reg) of an
increment (.DELTA.D) of the duty factor (D=t.sub.2 /T) of the
energization of the exciting coil 4 to an increment
(.DELTA.V.sub.reg) of a battery charging voltage in conjunction
with the illustration of FIG. 4. Firstly, the control
characteristic designated by (g) shows a voltage control method
according to a conventional one point detection system in which
100% excitation is effected when a battery charging voltage is
lower than the predetermined desired value (14.5 volts in this
case), while excitation is completely stopped when a battery
charging voltage is higher than the predetermined desired
value.
In contrast thereto, in the embodiment of this invention, a
suitable control characteristic may be chosen from the performance
characteristics indicated by (h), (i), (j), etc. in FIG. 4, for
example, in accordance with the setting of the reference voltage
V.sub.o, the triangular waveform voltage, and further a load
characteristic and an excitation characteristic of the generator 1,
and the duty factor D (a ratio of an excitation time to one
complete period) is adjusted continuously at every period depending
on the value of a battery charging voltage. Only, when a control
characteristic indicated by (i) or (j) is chosen and set, the ratio
.DELTA.D/.DELTA.V.sub.reg becomes small. Consequently, if a
relatively heavy electric load is connected to the generator 1
which is controlled under the above-mentioned condition, for
example, a generated voltage of the generator 1 is greatly reduced
depending on the load characteristic of the generator 1. In this
case, since the duty factor D is not increased so much as compared
with the great reduction in the generated voltage of the generator
1, much time is required before the generated voltage of the
generator 1 is restored to the predetermined desired voltage, and
hence it sometimes occurs that the generated voltage of the
generator 1 to be controlled flucturates with a big swing.
Therefore, it is desirable that the ratio .DELTA.D/.DELTA.V.sub.reg
may have a characteristic represented by a comparatively steep
straight line or curve so long as it does not give rise to a
phenomenon of hunting as described before.
In the embodiment of the present invention there has been chosen a
characteristic line as indicated by (h) in FIG. 4 whose slope is
set so as to effect the duty factor control of 0-100% within a
voltage variation of about .+-.0.2-0.3 volt with respect to a
predetermined desired voltage of about 14.5 volts. Further, the
crossing point of the characteristic lines (h), (i) and (j)
indicates a duty factor D.sub.s which gives an exciting current
necessary for obtaining a generated voltage of 14.5 V under the
conditions of a rated rotational speed and a rated load for a given
electric generator.
Next, an explanation will be given of embodiments of this invention
embodying the block construction shown in FIG. 2 by making
reference to FIGS. 5 to 9. Firstly, FIG. 5 shows concrete
exemplifying circuits for the blocks 21, 22, 24, 25, 26 and 28 and
the battery temperature detecting device 9. The charging voltage
detecting circuit 21 comprises a diode 211 connected to the
terminal S.sub.V and two diodes 212 and 213 connected to the
terminal B.sub.o, and it normally outputs a battery charging
voltage V.sub.B received at the terminal S.sub.V. The voltage
detecting circuit 24 comprises voltage dividing resistors 241 and
242 and a smoothing capacitor 243 and generates a divided voltage
V.sub.s. The battery temperature detecting device 9 disposed
outside the voltage regulator 5 comprises a thermistor 91 having
one of its terminals connected to a terminal of the battery 6 and
detecting temperatures of an electrolyte in the battery 6 and an a
adjusting resistor 92, and it supplies a detection voltage signal,
which has been obtained by detecting an electrolyte temperature and
a battery terminal voltage, to the terminal S.sub.T of the voltage
regulator 5. The temperature compensation circuit 22 comprises
resistors 221 to 223 and produces an additional correction voltage
signal for correcting a reference signal by adjusting a stabilized
voltage with a detection voltage signal supplied by the battery
temperature detecting device 9. The reference voltage circuit 25
comprises voltage dividing resistors 251 to 254 and produces a
desired reference voltage V.sub.o by the summation of a main
divided voltage given by voltage dividing resistors 251 to 253 and
a correction voltage supplied by the temperature compensation
circuit 22. The differential amplifier circuit 26 comprises an
operational amplifier 261 and resistors 262 to 264 and generates at
its output terminal X an output voltage V.sub.D which is obtained
by differentially amplifying both input voltages V.sub.s and
V.sub.o. The overvoltage detecting circuit 28 comprises an
operational amplifier 281, voltage dividing resistors 282 and 283
and input resistors 284 and 285, and it generates at its output
terminal Y a detection signal of zero level when the output voltage
of the charging voltage detecting circuit 21 reaches a
predetermined value which is considered to be an excessive
voltage.
Next, FIG. 6 shows a concrete example of the electric generation
detecting circuit 23. The electric generation detecting circuit 23
shown in FIG. 6 comprises a transistor 231, a capacitor 232 and a
resistor 233, which form a smoothing circuit, dividing resistors
234 and 235 and a collector resistor 236. The circuit 23 receives a
neutral point voltage, as an input signal thereto, from the
terminal N. When the neutral point voltage reaches a predetermined
value, the transistor 231 becomes conductive and produces an
electric generation signal of zero level at its output terminal
Z.
Next, FIG. 7 shows concrete exemplifying circuits for the blocks
40, 41 and 42 in FIG. 2. The key switch switching-on detecting
circuit 40 comprises a power transistor 401, resistors 402, 403 and
405, and another transistor 404. When the circuit 40 receives a
battery voltage from the terminal IG, the power transistor 401
becomes conductive to supply electric power to a succeding stage
and at the same time to render the transistor 404 conductive. The
terminal connection failure detecting circuit 41 comprises a power
transistor 411, resistors 412, 413 and 415, another transistor 414
and a diode 416. The circuit 41 operates in a way such that, only
when no battery voltage appears at the terminal IG and hence the
transistor 404 remains nonconductive, the transistor 414 becomes
conductive thereby to render the power transistor 411 conductive,
thus making it possible to supply a battery voltage from the
terminal L.sub.1 to the succeeding stage, to put its output
terminal W in the electric current drawing state of zero level, and
to force the transistor 536 in the third driver circuit 53 shown in
FIG. 8 to be nonconductive, thereby bringing the output terminal
L.sub.1 into an open state. The power supply circuit 42 comprises
diodes 421 and 422 and a constant voltage device 423. The circuit
42 operates to regulate an input voltage thereto at a predetermined
constant voltage V.sub.c (for example, 7 volts) and to supply it to
each of the circuits. The constant voltage device 423 comprises a
publicly known circuit containing a Zener diode, etc.
Next, FIG. 8 shows mainly concrete exemplifying circuits for the
blocks 32, 33, 51, 52 and 53 shown in FIG. 2. Firstly, the initial
excitation circuit 32 comprises a NAND gate 321 and an inverter
gate 322, and the circuit 32 is controlled by an electric
generation signal coming from the terminal Z. The first driver
circuit 51 comprises AND gates 511 and 515, a delay circuit 512,
NAND gates 513 and 514, an inverter gate 516 and a power transistor
517. The logic circuit 33 comprises a NOR gate 331, inverter gates
332 and 334 and a NAND gate 333 and is controlled by an overvoltage
detection signal from the terminal Y as well as an electric
generation signal from the terminal Z. The third driver circuit 53
comprises NAND gates 531 and 533, a delay circuit 532, an AND gate
534, an inverter gate 535 and a power transistor 536. The second
driver circuit 52 comprises an OR gate 521, a NOR gate 523, a delay
circuit 522, a NAND gate 524, an AND gate 525, transistors 526 and
527, a diode 528 and an inverter gate 529. The second driver
circuit 52 is controlled by an electric generation signal supplied
from the terminal Z.
Next, FIG. 9 shows a concrete example of the triangular waveform
generator circuit 27. The triangular waveform generator circuit 27
comprises transistors 271, 272, 274 and 280, a charge-and-discharge
capacitor 273, constant current sources 275 and 276, reference
voltage forming resistors 277 and 278, a diode 279, etc. The
triangular waveform generator circuit 27 outputs a triangular
waveform voltage V.sub.OUT by repeating a charging operation with a
constant charging current i.sub.1 +i.sub.2 during each time period
until a voltage across the capacitor273 reaches a divided voltage
established by the resistors 277 and 278 as well as a discharge
operation with a constant discharge current i.sub.3 -i.sub.1 during
each time period until the voltage across the capacitor 273 reaches
a forward voltage of the diode 279 (here, it is preset beforehand
that the relation i.sub.3 =i.sub.2 holds).
Now, a summarized explanation will be given of the operations of
the above-described concrete circuits, especially, those of the
circuits of the main parts of the apparatus of this invention shown
in FIG. 8. In a first stage where the key switch 7 has been
switched on but the generator 1 is generating no electromotive
force, the transistor 231 in the electric generation detecting
circuit 23 shown in FIG. 6 is in a nonconductive state and its
output terminal Z stays at "1" level. Normally, at this time there
is produced no overvoltage signal, so that the output terminal Y of
the overvoltage detecting circuit 28 in FIG. 5 is at "1" level, and
hence the AND gate 511 is put in a closed state, which causes the
output of the NAND gate 514 to stay at "1" level. Then, the on-off
control of the transistor 517 is effected by a pulse signal (an
oscillation signal) which is generated by the triangular waveform
generator circuit 27 and the waveform shaping circuit 29 and
supplied through the NAND gate 321, the AND gate 515 and the
inverter gate 516, thereby causing an intermittent initial exciting
current to flow through the exciting coil 4 connected to the output
terminal F. Since the terminal Z is at "1" level, the output of the
NAND gate 333 in the logic circuit 33 takes "1" level. Further,
since the delay circuit 532 outputs a zero level signal during an
initial predetermined time period and normally a "1" level signal
is supplied to the terminal W, the output of the AND gate 534 is at
"1" level. Consequently, the output of the NAND gate 531 takes zero
level to give a "1" level signal to the base of the transistor 536,
thereby causing the transistor 536 to conduct. Further, once the
transistor 536 has become conductive, the output signal at the
collector of the transistor 536 is fed back to an input to the NAND
gate 533 thereby to cause the NAND gate 531 to maintain its output
at zero level and hence the transistor 536 to continue conducting.
Thus, the indicating means 8 connected to the output terminal
L.sub.1 is lit to indicate that the generator 1 has not yet started
electric generation. Further, at the same time, the OR gate 521 in
the second driver circuit 52 outputs a "1" level signal to render
the transistor 526 conductive, while, the AND gate 525 outputs a
"1" level signal to render the transistor 527 nonconductive,
thereby putting the output terminal L.sub.2 into an electric
current supplying state.
Next, when the engine has started its operation and the magnitude
of the voltage of the neutral point of the generator 1 has reached
a predetermined value, the transistor 231 in FIG. 6 becomes
conductive and its output terminal Z takes zero level. As a result,
the AND gate 511 in the first driver circuit 51 in FIG. 8 is
opened, while the NAND gate 321 in the initial excitation circuit
32 is closed and continues to generate a "1" level signal at its
output. Thereafter, the operation of the first driver circuit 51 is
controlled by an output signal from the comparator circuit 30.
Assume that the output of the comparator circuit 30 takes "1"
level, for example. Since the delay circuit 512 continues to output
a zero level signal thereby to maintain the output of the NAND gate
513 at "1" level, immediately after the output of the comparator
circuit 30 has changed to "1" level, and further no overvoltage is
detected at this time, so that the output terminal Y of the
overvoltage detecting circuit 28 in FIG. 5 stays at "1" level, the
output of the NAND gate 514 takes zero level thereby to render the
transistor 517 conductive, which, in turn, renders the exciting
coil 4 connected to the terminal F energized. Thus, when the
terminal F has been changed to zero level, a feedback path from the
collector of the transistor 517 to an input to the NAND gate 513
operates to maintain the output of the NAND gate 513 at "1" level
even after the output of the delay circuit 512 has changed to "1"
level. On the other hand, if the output of the comparator circuit
30 takes zero level, the output of the NAND gate 514 and hence that
of the AND gate 515 take "1" level thereby to render the transistor
517 nonconductive and hence the exciting coil 4 de-energized.
Further, if an excessively high voltage occurs on the battery
charging line, the overvoltage detecting circuit 28 in FIG. 5
detects it and operates to change its output terminal Y to zero
level, which forces the output of the NAND gate 514 to become "1"
level and hence causes the transistor 517 to become nonconductive.
At the same time, a frequency-divided pulse signal generated by the
frequency divider circuit 31 is sent through the NOR gate 331 and
passes through the NAND gates 333 and 531, which then causes the
ON-OFF operation of the transistor 536 and hence the flashing
operation of the indicating means 8 connected to the terminal
L.sub.1.
Further, since the terminal Y remains at "1" level so long as no
overvoltage appears, when the terminal Z takes zero level, the
output of the NOR gate 331 is forced to take zero level, and hence
the output of the NAND gate 333 is also forced to take zero level.
As a result, the output of the NAND gate 531 in the third driver
circuit 53 is forced to take "1" level, thereby rendering the
transistor 536 nonconductive, the terminal L.sub.1 de-energized and
hence the indicating means 8 put out. Further, when the terminal Z
is at zero level, the output of the AND gate 525 in the second
driver circuit 52 always takes zero level, which renders the
transistor 527 conductive and thereby puts the terminal L.sub.2
into an electric current drawing state. Since the potential of the
terminal L.sub.2 in the electric current drawing state is fed back
through the inverter gate 529 to an input to the NOR gate 523 to
give "1" level thereto, two inputs to the NOR gate 523 take zero
level and "1" level, respectively, which causes the output of the
NOR gate 523 to take zero level. Thus, since both inputs to the OR
gate 521 become zero level, the output of the OR gate 521 also
takes zero level, which assures maintainance of the transistor 526
in a nonconductive state.
In the construction of the above-described embodiment, the initial
excitation circuit 32 is connected to the first driver circuit 51
to give the latter an oscillation pulse signal, which was obtained
by waveform-shaping a triangular waveform voltage generated by the
triangular waveform generator circuit 27, directly without passing
the comparator circuit 30, thereby to cause initial excitation.
However, a construction for controlling an intermittent operation
of the first driver circuit 51 is not limited to the
above-described one. In another construction shown in FIG. 10, for
example, the initial excitation circuit 32 is connected to an input
to the comparator circuit 30, whereby in the state of no electric
generation, that is, when the terminal Z is at "1" level, the
transistor 323 is rendered conductive to cause the voltage at the
point A forcibly to be set to a constant voltage to be determined
by the diodes 324 and 325, irrespective of the state of the output
of the differential amplifier circuit 26. With the above-described
construction, the comparator circuit 30 makes a comparison between
a triangular waveform voltage from the triangular waveform
generator circuit 27 and the voltage at the point A to produce an
oscillation pulse signal having the same period as that of the
triangular waveform voltage and a constant duty factor determined
by the relative magnitude of both voltages to be compared. Thus, it
is possible to obtain the same functional effect as that brought by
the above-described embodiment. Besides the foregoing, with a
further construction in which the voltage of one of the inputs
[either the reference voltage (V.sub.o) side or the detected
voltage (V.sub.s) side] to the differential amplifier circuit 26 is
made to take a fixed value in response to a signal from the
electric generation detecting circuit 23 so that the output voltage
of the differential amplifier circuit 26 may take a constant value
only when electric generation has not yet taken place, it is also
possible to obtain the same functional effect.
The above-explained voltage control apparatus embodying this
invention has various features as shown below:
(1) By applying an oscillation signal, which changes on-and-off at
a constant rate, to the first driver circuit 51 thereby to limit an
exciting current from the moment of switching-on of the key switch
7 to the build-up of the generator 1, it is possible to limit an
initial exciting current to a value necessary for assuring the
build-up of the generator 1 without using initial exciting current
limiting resistors, etc. and at the same time to prevent the
battery from fully discharging in a short time when a driver has
failed to switch off the key switch 7.
(2) In this invention, the exciting coil 4 is rendered energized
and de-energized always at a constant rate by comparing a voltage
corresponding to a difference between a battery charging voltage
and a reference voltage with an output voltage of the triangular
waveform generator circuit 27 and thereby causing the output stage
transistor in the first driver circuit 51 to turn conductive and
nonconductive depending on the relative magnitude of both
comparison voltages. Therefore, the voltage control apparatus of
this invention differs from an apparatus of the conventional type
which makes a direct comparison between a charging voltage and a
reference voltage to effect an on-off operation at an unstable
rate. Consequently, it is possible to prevent hunting of a charging
voltage or a charging current and hence undesirable oscillation of
an indicating needle of a voltmeter or ammeter.
(3) Since this invention provides redundancy to permit power supply
to the control part also from the terminal L.sub.1 connected to the
key switch 7 via the load 8, other than from the terminal IG, by
detecting whether the key switch 7 is in a closed state or not and
power supply is effected normally through the terminal IG or not,
it is possible to maintain the function of electric generation of
the generator 1 even if contact failure due to a defective
connector, etc. or coming-off of a lead wire terminating lug occurs
at the terminal IG, or a lead wire end falls off from the terminal
IG to ground.
(4) The terminal L.sub.2, which is used to inform other apparatuses
as to whether the generator 1 is in the state of electric
generation, may be made to operate as an electric current supplying
or drawing terminal depending on the state of electric generation,
and it is possible to select freely the other apparatuses without
causing any interference with the input impedance of each of such
apparatuses.
(5) The construction that the circuit 28 for detecting a charging
voltage is provided other than the voltage detecting circuit 24
comprising a voltage smoothing capacitor thereby to render the
first driver circuit 51 inoperative and to cause the electric
generation indicating means 8 to flash, as soon as a charging
voltage has risen abnormally, brings the following effects:
(a) Since it is possible to render the first driver circuit 51
inoperative without any time delay, which might be caused by the
existence of a capacitor, when the end of a lead wire has come off
from a battery charging terminal and a generated voltage has risen
abruptly, the output transistor of the first driver circuit 51 can
be prevented from being damaged by a possible heavy current flowing
therethrough; and
(b) Since it is possible to warn a driver of the occurrence of an
abnormal state distinctly by the flashing operation of the electric
generation indicating means 8 when a generated voltage has risen
abruptly due to a short-circuit accident of the exciting coil 4, it
is possible to prevent a dangerous state such as the breakage of
headlight bulbs, etc. from being caused by the overvoltage.
(6) As a protective measure against an accident where an abnormally
high voltage is impressed on one of the output terminals F, L.sub.2
and L.sub.1 when the corresponding one of the first, second and
third driver circuits 51, 52 and 53 is in operation, it is possible
to render the corresponding one of the switching circuits 35, 37
and 39 in the respective driver circuits inoperative thereby to
protect the elements in the switching circuits against such an
accident.
(7) It is possible to compensate a battery charging voltage for
temperature variations so that it may have an optimum mutual
relation by correcting a reference voltage to be compared with the
battery charing voltage to take a suitable value in response to
temperatures of an electrolyte in the battery.
In general, the build-up of a voltage generated by the generator 1
is determined by the product of an exciting current (an exciting
magnetic flux) and the number of revolutions per unit time of the
generator 1. So far as the oscillation signal has a fixed period,
the higher the duty factor is, the greater becomes the average
value of the exciting current and the lower becomes the build-up
rotational speed. Therefore, a higher duty factor is effective in
reducing the build-up rotational speed, but, on the other hand, it
causes an increased amount of discharge of the battery because of
the increased exciting current when a driver fails to switch off
the key switch 7. Accordingly, the condition of oscillation of the
triangular waveform generator circuit 27 should be determined
optionally in accordance with the presetting or requirements of the
build-up rotational speed of the generator 1, the rising
characteristic of an exciting current, etc.
Here, the triangular waveform generator circuit 27 used in this
invention is not limited to an electric circuit for generating a
triangular waveform voltage in the strict sense of the word, but
may be any electric circuit so long as it generates a voltage
having a fixed waveform which always increase or decrease regularly
at constant periods. For example, it may be an electric circuit
which generates a voltage of an exponential waveform by utilizing
charge and discharge of a capacitor, or one which generates a
voltage of a stepped waveform by using the output signal of an
electronic counter circuit.
In the embodiment shown in FIG. 4, the relation of the duty factor
D versus the regulated voltage or battery charging voltage
V.sub.reg has been preset especially to be linear. However, taking
into consideration that the characteristic of the relation of the
exciting current versus the generated voltage of the generator 1 is
of a cubic function, it is possible to attain more effective
control of electric generation by changing the inclined portion of
the waveform of the triangular waveform voltage to a cubic curve,
thereby presetting the relation of the duty factor D versus the
regulated voltage V.sub.reg to be a cubic function.
As other examples of the embodiment of this invention, the electric
generation detecting circuit 23 may detect a state of electric
generation by detecting the output of the armature winding 3 or
that of the rectifier 2 other than by the detection of the neutral
point voltage of the generator 1. Here, the time when the build-up
of a generated voltage is completed corresponds, in general, to the
time when the rotational speed of the engine has exceeded its
idling rotational speed (600-900 RPM) after the engine has started
rotating. Such a time may be determined by taking into
consideration the magnitude of an initial exciting current, the
state of magnetization of the rotor of the generator 1, etc.
Therefore, it may also be possible to detect the state of electric
generation indirectly by the rotational speed of the engine,
etc.
Further, the time of switching-on of the key switch 7 is generally
understood as the time at which a driver has electrically connected
an ignition terminal of the key switch 7 to a battery terminal
thereof. In this invention, however, the time of switching-on of
the key switch 7 is not necessarily limited to the above-mentioned
situation, but it also includes the time when a driver has
electrically connected an accessory terminal or a starter terminal
of the key switch 7 to the battery terminal thereof.
Further, in the above-described embodiment of this invention, the
indication of the results of the electric generation detection and
the overvoltage detection is effected to enable the discrimination
of both states from each other, namely, by the simple lighting of
an indicating lamp in the former and by the flashing operation of
an indicating lamp in the latter. However, the above-mentioned
object may be accomplished by other means, for example, by
switching the flashing frequency of an indicating lamp, or by
making use of different indicating elements such as a liquid
crystal, a PLZT element (a ceramic element having an
electrophotoluminescence effect), etc. other than an incandescent
lamp and by switching an applied voltage (current) in response to
both states as mentioned above thereby to vary an indicating colour
of each of such indicating elements.
As described above, the overvoltage detecting circuit 28 detects
the state of overvoltage of a generated voltage or a battery
voltage. The state of overvoltage represents a case where a voltage
which overchanges the battery appears, and also a case where there
occurs a voltage having a high value which is undesirable for
various electric loads, especially, electronic circuits, connected
to the terminal of the battery.
As is apparent from the foregoing descriptions, this invention
provides a voltage control apparatus for electric generators for
vehicles wherein the initial excitation circuit generates an
oscillation signal for the purpose of initial excitation during a
time interval from the switching-on of the key switch to the
arrival of the electric generator at a predetermined condition of
electric generation and supplies the oscillation signal to the
driver circuit and thereby makes the driver circuit supply an
initial exciting current to the exciliting coil, then, after the
above-mentioned time interval, the differential amplifier circuit
forms a detected voltage corresponding to a difference between a
reference voltage and a generated voltage or a battery charging
voltage, the triangular waveform generator circuit forms a
triangular waveform voltage oscillating with a predetermined
voltage swing and at constant periods, and a comparison signal
obtained by the magnitude comparison between the above-mentioned
detected voltage and the triangular waveform voltage is supplied to
the driver circuit, thereby continuously controlling the exciting
condition of the electric generator depending on the relation
between the above-mentioned two voltage signals and taking the
response characteristic of the control system into consideration.
The above-described construction of the voltage control apparatus
of this invention brings excellent advantages such that an initial
exciting current can be limited without using any conventional
initial exciting current limiting power resistor, whereby a
discharge current can be reduced and overdischarge of the battery
can be prevented when a driver has failed to switch off the key
switch, and a generated voltage (or a battery charging voltage) can
be monitored and controlled always at constant periods without
being affected by variations of the rotational speed of the
electric generator and a generated voltage (a battery charging
voltage), and hence this voltage control apparatus can be free from
a response delay which is incidental to an electric generation
control system and also enables high precision voltage control even
when the electric generator is operating at low rotational speeds
or under a light load. Further, since this invention renders the
use of a power resistor unnecessary, it is possible to make
assembly work easy and to design electric circuits which can be
conveniently fabricated with IC's.
* * * * *